Immune cells in the gut protect against diseases

Intestinal immune cells crucial for the body's defenses

11.05.2011

The intestine plays a crucial role not only in digestion but also in the immune system. Special lymphocytes in the intestine are of particular importance, according to US researchers Lora Hooper from Southwestern Medical Center, University of Texas, Dallas, USA, in the latest issue of the journal „Proceedings of the National Academy of Sciences, PNAS“

Certain lymphocytes in the gut serve to ward off pathogens and bacteria directly on the intestinal wall, so the statement of the US scientists. The defense function of the lymphocytes is particularly important in the first three to four hours after the entry of the pathogens, said Lora Hooper and colleagues. If the protective function is disturbed, severe chronic bowel disease could result.

Immune cells in the gut prevent the spread of pathogens
The special importance of the lymphocytes in the intestine for the immune defense, the US researchers have investigated using laboratory experiments in which they were genetically engineered mice that could produce no corresponding lymphocytes and healthy mice pathogens (salmonella) in the diet record. They then observed the response of the immune system, with the concentration of spleens in the spleen three hours after salmonella uptake was 100-fold higher in mice without lymphocytes than in normal mice. However, 24 hours after admission, the differences in salmonella exposure decreased again as the remaining parts of the immune system began to control the pathogens, the US researchers report. The intestinal lymphocytes therefore play a special role, especially in the first hours after the infestation of the pathogens.

Intestinal lymphocytes form antibodies and alert immune cells
According to the US scientists, special lymphocytes in the intestine produce antibodies as soon as they have contact with bacteria in the intestinal mucosa. It releases so-called lectins (bacteria killing proteins) and messengers that alert other immune cells, explained the US researchers. Thus, in the first hours after the entry of the pathogens their spread can be controlled and effective immune control can be ensured, said Lora Hooper and colleagues. A deficiency of the corresponding intestinal lymphocytes and other disorders of the protective function described, could also be the cause of inflammatory bowel diseases such as ulcerative colitis or Crohn's disease according to the assumptions of the US researchers. For in the case of chronic inflammatory bowel disease, the balance between the bacteria in the intestine and the body's defenses play a special role, explain the US scientists. On the one hand, the body has to accept the bacteria as a natural component of a healthy intestinal flora, and on the other hand, it must prevent the germs from entering the intestinal mucosa in order to prevent infections.

Research intensified - discovered association between overweight and intestinal type
The importance of the interaction between bacteria and fungi of the intestinal flora with the body's own defenses has been the subject of extensive studies in recent years, focusing not only on the effects of the defense against pathogens, but also, for example, a connection of certain intestinal types with the risk of obesity and obesity was studied. For example, a study led by the European Molecular Biology Laboratory (EMBL) in Heidelberg came to the conclusion that three different types of germ populations can be determined in the human gut, depending on the type of bacteria present. These also regulate the individual food use and determine whether a person tends to become overweight or obese (obese), reported the researchers of the EMBL in the journal „Nature“. However, the now discovered effects of intestinal lymphocytes could potentially help to develop new therapies for the treatment and prevention of diseases, „if we understand how the bacterial defense of these immune cells can be strengthened“, emphasized the US researchers. (Fp)

Read about intestines and defenses:
Majority of Germans have intestinal fungi
Diverticula: Fiber facilitates the intestine
Bowel type crucial for obesity?
Intestinal dysbiosis: Bacteria against bacteria

Picture: Sigrid Rossmann